Apparatus for water purification

ABSTRACT

A reservoir of purified water is prepared from a natural body of water by constructing a prefiltering levee through the water to segregate the reservoir area from the remainder of the water body, pumping water from the reservoir area into the remainder, cleaning the floor of the reservoir area if necessary, installing a water purification unit in the reservoir, and then allowing the water to filter through the levee from the remainder of the water body into the reservoir for continuous further purification and recirculation by the installed unit. The water purification unit includes a mixing chamber, a filtering chamber, skimming means for intaking surface water into the mixing chamber, submerged inlets for intaking water into the mixing chamber from below the water&#39;&#39;s surface, a pump for passing water from the mixing chamber through the filtering chamber, and outlet means for passing the filtered water directly back to the reservoir. The preferred skimming means comprises a mobile skimming gutter to insure a constant intake of surface water at various reservoir water levels and a submersible pump is preferably positioned in the mixing chamber to force the mixed water through one or more filter cells provided in the filtering chamber. The outlet means are preferably disposed to set up recirculation currents using the earth&#39;&#39;s rotation effect, and means are also provided for backwashing the filter cells. To insure that the pump does not run dry the submerged inlet flow is preferably float modulated to provide the full capacity of the pump if the skimmed flow is temporarily reduced. Various purifying chemicals may be added to the processed water in its passage through the unit, and in a modified form of the invention, a portion of the purified water is passed back to the remainder of the water body for progressive purification thereof.

United States Pat ent [54] APPARATUS F OR WATER PURIFICATION 10 Claims,9 Drawing Figs.

52 us. Cl 210/167 [51] Int. Cl. 301d 35/26 [50] Field of Search 210/169,167, 290

[56] References Cited UNITED STATES PATENTS 1,979,623 1 1/1934 Hunter210/169 2,302.450 11/1942 Laughlin 210/290 2,502,052 3/1950 Landon etal.... 210/169 3.169.920 2/1965 Payne 210/169 3,268,079 8/1966Sharrow,.1r. 210/169 Primary E.raniiner Reuben Friedman AssistantExaminer-T. A. Granger Attorney-Synnestvedt & Lechner ABSTRACT: Areservoir of purified water is prepared from a natural body of water byconstructing a prefiltering levee through the water to segregate thereservoir area from the remainder of the water body, pumping water fromthe reservoir area into the remainder, cleaning the floor of thereservoir area if necessary. installing a water purification unit in thereservoir, and then allowing the water to filter through the I leveefrom the remainder of the water body into the reservoir for continuousfurther purification and recirculation by the installed unit. The waterpurification unit includes a mixing chamber, a filtering chamber,skimming means for intaking surfacewater into the mixing chamber,submerged inlets for intaking water into the mixing chamber from belowthe water's surface, a pump for passing water from the mixing chamberthrough the filtering chamber, and outlet means for passing the filteredwater directly back to the reservoir. The a preferred skimming meanscomprises a mobile skimming gutter to insure a constant intake ofsurface water at various reservoir water levels and a submersible pumpis preferably positioned in the mixing chamber to force the mixed waterthrough one or more filter cells provided in the filtering chamber; Theoutlet means are preferably disposed to set up recirculation currentsusing the earths rotation effect, and means are also provided forbackwashing the filter cells. To insure that the pump does not run drythe submerged inlet flow is preferably float modulated to provide thefull capacity of the pump if the skimmed flow is temporarily reduced.Various purifying chemicals may be added to the processed water in itspassage through the unit, and in a modified form of the invention, aportion of the purified water is passed back to the remainder of thewater body for progressive purification thereof.

PATENTEDAUB 312m 3596,7658

SHEET 1 OF 6 INVENTOR GEORGE R. WHITTEN, JR.

BY WIPMSML,

ATTORNEYS PATENIEDAUB 3m: 3596.768

sum 2 OF 6 BUILD PREFILTERING LEVEE TO SEGREGATE RESERVOIR FROMREMAINDER PUMP WATER FROM RESERVOIR TO REMAINDER INSTALL WATERPURIFICATION UNIT CENTRALLY WITHIN RESERVOIR CLEAN RESERVOIR (OPTIONAL)ALLOW WATER TO FILTER INTO RESERVOIR PROCESS RESERVOIR WATER THROUGHUNIT RETURN PORTION OF PROCESSED RESERVOIR WATER TO REMAINDER (OPTIONAL)FIG. 3

INVENTOR GEORGE R. WHITTEN, JR.

BY W PMfiM ATTORNEYS PATENIED Am; 3197! SHEET 3 OF 6 INVENTOR RM J: N E

H w l G. R- O E G ATTORNEYS PATENIEU nus 3 Ian SHEET k 0F 6 was INVENTORFIG. 7

GEORGE R. WHITTEN,JR

lamwitw ATTORNEYS PATENTEU Aus awn sum 5 OF 6 mufififiuwnnnnnnnnnnnnnnmv nununnnnunu m2 iiiii- 8 Mg U 3% w; mm

Nm vm INVENTOR GEORGE R. WHITTEN,JR.

ATTORNEYS APPARATUS FORWATER PURIFICATION BACKGROUND or THE INVENTIONThis invention relates to water purification and is more particularlydirected to a method of purifying segments of bodies of pollutedwaterand a water purification unit having particular utility inpracticing such a method.

The ever increasing menace of water-pollution has seriously decreasedthe number of natural'water bodiesavailable for potable water supply,recreational swimming and industrial needs. In order to provide suchfacilities for our ever expanding needs, many municipalities haveattempted to build largescale water-processing plants and artificialswimming pools capable of purifying high volumesof water such plants andpools have proven in many cases to be prohibitively expensive to handlethe demands presented, and in respect to recreational facilities, haveproven to be far less pleasurable swimming areas in contrast to naturalbodies of water such as lakes, ponds and the like.

Previous attempts have been made to purify polluted bodies 'of-water.These prior attempts,- however, have been in the main unsuccessfulbecause of the magnitude of the problem of purifying an entire body ofwater. Even in the cases when such efforts have been successful, theyhave produced a concomitant disadvantage in that the-body of water isthen frequently unfit for most wild life, thereby having shortcomingsfrom a conservation point of view.

, 7 SUMMARY OF THEINVENTION The present invention contemplates awaterpurification unit for segregating a reservoir area from'theremainder of a natural body of water and then installing the waterpurification unit in, the reservoir to purify that portion to produce areservoir of pure water for recreational or water supply purposes. Usingthis invention, municipalities can develop water supply reservoirs and/rswimming facilitiesfrom lakes. ponds and streams which are presentlyuseless due to contamination and pollution. When the reservoir is usedfor swimming, the pleasure derived from its use is enhanced because thenatural shoreline and associated virtues of a natural body of water areretained. In smaller bodies of water (either natural or artificial)segmenting may not be necessary and the entire water body may bepurified by the water purification unit of the invention.ln eithermanner a polluted or contaminated body of water can be reclaimed toprovide purified, treated water for a town or city water supply,recreational swimming or industrial needs.

In accordance with theinvention a prefiltering levee such asof bank-rungravel or other suitable filtering material is con- 2 pointfand merelyinstalled in the prepared site. If desired,.a number of theprefabricated units may. be installed to purify larger reservoirs. Theinvention, therefore, greatly reduces the cost of providing pure watersupply and mass recreational 51 swimming areas from presently uselesspolluted natural water DETAILED DESCRIPTION OF THE INVENTION Theseobjects and other objects and advantages of the present invention willbecome moreapparent as the detailed description thereof proceeds withcontinued reference to the structed within a body of water to segregateareservoir portion from the remainder thereof. The water within thereservoir portion is then pumped back into the remainder of the lake,pond or stream. The floor of the reservoir may be cleaned as by dredgingto remove contaminants if necessary, and covered with an inert materialsuch as crush stone, sand or the like. A water purification unit is theninstalled in the reservoir area and the pumping means removed to allowwater from the remainder of the lake to pass through the prefilteringlevee into the reservoir. In its passage through the levee, most of theheavy suspended particles are removed from the water. A second filteringpass is provided for this water by the water purification unit of theinvention. The unit may be installed in any body'of water without theneed of any external piping to or from the water body to intake ordischarge water. By incorporating inlet and outlet means in the unititself, the costly and time consuming process of individual design foreach water supply and recreational facility. as well as on shoreequipment buildings, external piping and the high cost of constructionlabor presently required to produce comparable pure water reservoirs areeliminated. Each unit'is designed to purify a drawings wherein:

FIG. 1 is a plan view of a pure water reservoir prepared in accordancewith the invention. I

FIG. 2 is a sectional view along line 2-2 of FIG. I.

FIG. 3 is a block diagram of the method employed to produce thereservoir shown in FIGS. 1 and 2.

FIG.-4 is a partially diagrammatic plan view of the water purificationunit shown in FIGS. 1 and 2'.

FIG. 5 is a cross section of the unit taken along line 5-5 of FIG. 2.

FIG. 6 is a view along line 6-6 of FIG. 5.

' no. 7 is a view along line 7-7 of FIG. 5.

FIG. 8 is a view along line 8-8 of FIG. 5.

FIG. 9 is a view similar to FIG. 7 showing a modified form of the unitto progressively decontaminate the body of water ad- 'jacent thereservoir.

With reference now to the drawings wherein like reference numerals areused to identify the same elements in the various views, and initiallyreferring to FIGS. 1, 2 and 3, a typical pure water reservoir producedin accordance with the invention is therein shown. In preparing thisarea from a polluted body of water, such as a lake, indicated at 10, aprefiltering levee 12 such as a bank-run gravel, crushed stone or sand,is constructed from one point on the shore continuously through the lake10 to a second point on the shore to segregate a reservoir area'l4 fromthe remainder of the lake 16. The water from the reservoir 14 was thencontinuously pumped into the remainder 16 of the lake 10 to bring thereservoir area to a substantially dry preparation state. While in a drystate, the floor 18 ofthe reservoir area 14 is, if necessary, cleaned ofundesired materials such as decayed foliage, mud and various kinds ofdebris and rubbish, so as to both decontaminate the area and prepare itfor public use. During this dry preparation period, a foundation 20 ofconcrete or the like for a water purification unit 22 (to be laterdescribed in' detail) is constructed in the floor 18 together with anumbilical cord for the unit comprising an underground power supplyconduit 24 and an underground waste conduit 26 leading from thefoundation to the shore. The water purification unit 22 is theninstalled on the foundation prepared for it, the floor 18 is coveredwith an inert material 28 such as crushed stone or sand, and the pumpingmeans are removed.

At this point, water from the lake portion 16 seeps through theprefiltering levee 12 to provide a first filtering pass for the waterentering the reservoir 14. After the water establishes its surface levelindicated at 30, the water purification unit 22 f continuously filtersand other wise purifies and recirculatcs it through the reservoir 14 inthe manner described hereinafter.

large volume of water to a degree of purity acceptable to It should beappreciated that a reservoir 14 of any size desired may be prepareddepending only on the size of the polluted lake, pond or the like 10selected and the configuration of the prefiltering levee provided. Thelevee 12 need not extend between two points on the shore but could evenbe formed centrally in the water body 10. By using a natural filteringmedia such as bank-run gravel which can be found in almost anygeographical area of our country, the reservoir 14 may be prepared fromreadily available materials. Moreover,

available to most municipalities such as trucks, bulldozers and the liketo build the levee l2, pumps to maintain the area in a dry state duringpreparation, and standard excavation or grad.- ing equipment to cleanthe floor 18. Thus, the site may be prepared from conventional materialsby using standard tools and unskilled labor in contrast to the high costnecessary to construct an artificial reservoir or pool of comparablesize.

If natural filtering media such as gravel is not available, however, thelevee 12 may also be prefabricated of plastic, wire mesh and othermaterial as a prefiltering assembly and installed at the site 14. Thepure water reservoir 14 may be used as a recreational swimming site oras a source of pure water for human or industrial consumption.Alternately, the invention'may be used to purify industrial waste waterbefore its return to the river or lake from whence it was taken. To ac-.complish the latter function, industrial waste water may be continuouslydumped into the main portion 16 of a pool or lake 10. In this instance,the pool is normally a natural or specially excavated cavity locatednear the original source of the industrial water. The levee 12 providesa first filtering pass for this water,'while' the unit 22 furtherpurifies it. The water may then be pumped from the reservoir 14 back toits original source. In its latter application the invention provides aneconomically feasible means for eliminating pollution from industrialsources.

The description will now focus on the preferred embodiment of the waterpurification unit 22 as shown in FIGS. 4 through 8. As best seen in FIG.5, the unit'is preferably formed with 'vertical sheet metal sides 32 todefine a partially submerged watertight inner compartment 34.Intermediate partition walls 36 and 38 preferably divide the innercompartment into three watertight chambers, namely, a mixing chamber 40,an intermediate control chamber 42 and a filtering chamber 44. The roofof the unit'is preferably a concrete upper deck slab 46 '(see FIGS. 4,6', 7 and 8) which provides ballast necessary to maintain the unit in apartially submerged position and may also function as an equipmentplatform in the nature of a raft on which diving boards and similarrecreational facilities typically indicated at 48 may be mounted ifdesired. An equipment room 50 is positioned on the upper deck slab 46 tohouse a means for adding purifying chemicals such as a conventionalchlorination unit 52 and also to cover an access hatch 54 to the controlchamber 42.

The floor 56 of the unit 22 is also fabricated of sheet metal and'isvertically spaced from the foundation by a plurality of verticallydisposed submerged inlet grated 58 which completely surround the bottomof the unit to define a cavity 60 beneath the floor 56. The unit 22 issecured to the foundation 20 as by bolts passing between angle irons 62,the submerged inlet grated 58 and the foundation 20, respectively.

Looking now at FIGS. 6 and 7, a skimming ring or gutter 64 is positionedat the waters surface around the upper periphery of the walls 32 and istelescopically supported thereon by a plurality of preferably equallyspaced and substantially vertical extensible conduit members 66. Thegutter has an outer spillover lip 68 over which surface water from thereservoir 14 may pass into the gutter 64. Perforated skimming gutterintake grills 70 are provided to remove solid matter, such as leaves,floating on the waters surface 30. The skimmed water flow then passesthrough the extensible conduit members 66 down to a peripheral skim'medwater collection duct 72 which is fluidly connected through an aperture.74

i (see FIG. 8) in the wall 32 to the mixing chamber 40.

Since most contaminants enter a body of water from its surface, thepublic health regulations accordingly require that at least half of thewater processed by a filtration unit for a municipal swimming facilityshould comprise water skimmed from the surface. Tocomply with thisrequirement for use in the context of natural water bodies wherein thelevel 30 ofthe water may vary widely due to seasonal variations of thewater shed, heavy rains, wave action, and rapid ingress and egress ofswimmers, it is necessary to vary the height of the gutter 64 inresponse to such surface level changes. To that end, a layer of buoyantmaterial 76 such as cork is adhered to the bottom of the gutter 64 andan air chamber 78 is also formed around the bottom of the gutter ring toroughly maintain the effective specific gravity of the gutter 64 andextensible conduit 66 assembly at neutral buoyancy at designgutter flow.

As seen in FIG. 6, the air chamber 78 is a channel having a bottomopening. A flexible conduit or hose 80 opens into; the upper portion ofthe air chamber 78 and is in fluid communication with an air compressor82 positioned within the control chamber 42. A three-way. solenoidactuated valve 84 having one port open to the atmosphere is provided inthe line 80 intermediate the chamber 78 and compressor 82 to regulatethe airflow to the chamber 78. The valve 82 is in turn actuated by alevel-sensing and transmitter unit 86 typically of the,

diaphragm type manufactured by the Industrial Division of Honeywellunder Specification S 8 l6-5, which unit senses the water level in themixing chamber and is adapted to electrically switch the solenoid valve84 to add or exhaust air from the air chamber 78 to provide a finecontrol over the effective specific gravity of gutter assembly. Forexample, when the skimming flow rate is too low, indicating that thegutter 64 is too high in the water, the sensing unit 86 will sense adecrease in the mixing chamber lever and switch the valve 84 to exhaustair from the air chamber 78, thereby lowering the gutter 64 andconcomitantly increasing the skimming flow rate, On the other hand, whenthe skimming flow rate is too high, indicating that the gutter 64 is toolow in the water and perhaps that the skimming inlet grill 70 is evenbelow the water surface, the sensing unit 86 will sense the resultingincrease in the mixing chamber level and switch the valve 84 to add airto the air chamber, thereby raising the gutter 64 to decrease theskimming flow rate. Thus, means are provided for automatically insuringa substantially constant skimming flow rate into the mixing chamber 40.

Water is also taken in by the unit from the lower or submerged portionof the reservoir 14 through the submerged inlet grated 58, which watercollects in the bottom cavity 60 and passes into the mixing chamber 40through conduits 86 extending through the floor 56 into the mixingchamber 40. It should be apparent that unless the submerged inlet flowrate through the submerged inlet conduits 86 are regulated, the waterlevel in the mixing chamber would soon reach the water level 30 of thereservoir I4. This result would be highly undesirable because theskimming flow rate would then fall to zero. To prevent this result,modulating valves 88 with their associated floats 90 are provided theinner ends of the submerged inlet conduits 86 to partially close theconduits 86 for all mixing chamber water levels 92 above a predeterminedlevel. Therefore, for any level 92 above that predetermined level, thefloats 90 will partially close the valves 88 so that most of the waterbeing processed represents the skimming flow rate. For optimumrecirculation of the reservoir water, the ratio of skimming flow rate tosubmerged inlet flow rate should be about 3: l. Thus, the modulatingvalves 88 should be set to always allow a minimum of 25 percent of theoverall unit flow rate to pass through the submerged inlet conduits 86,regardless of the mixing chamber level. On theother hand, the gutter 64should be designed and positioned to provide 75 percent of the totalflow rate.

As best seen in FIG. 8, a submersible pump and motor 94, typically ofthe type produced by Flygt Corporation of Sweden, is mounted within themixing chamber 40 below the predetermined level maintained by themodulating valves 88 to continuously pump intaken water from thatchamber to the filtering chamber 44 via a main supply pipe 96 connectedat one end to the pressure side'of the pump 94 and opening at its otherend into a main filter inlet pipe 98. To insure that the pump. 94 isalways submerged, the submerged inlet conduits 86 should (when fullyopen) accommodate a flow equal to the total flow of the unit 22 and themodulating valves 88 should open these conduits when the mixing chamberlevel 92 falls to the point at which the pump is barely submerged. Thisinsures a constant supply for the. pump 94 during repositioning or anymalfunctioning of the skimming gutter. assembly. toavoid inadvertentstoppage of the continuous operationv of. the unit. Moreover, byemploying a submersiblepump and. insuring that-it is constantlysubmerged to avoid its becoming overheated or running dry, the unit 22may be more compactly designed and operates more quietly than it wouldif a dry pump were used.

As indicated in FIG. 8 by solid arrows v100, the water then passesthrough the filter inlet pipe 98'toenter'the upper portion of thefiltering chamber 44. Three superposed filter layersor'cellsl02-typically of sand, are provided within the filteringchamber44 upon perforated plates 104. Contaminants are removed from thewater as it passes through the sand layers 102 under the force ofthepump 94 andof gravity in aconventional manner. The number andsurface. area. of the filter layers 102 provided, may, of course, bevaried in accordance with the overall flow rate of theapparatus and thedegree of purity required. Present generally accepted practice is to toenable the filtered water to then flow to theoutlet duct 112 forimmediate reentry to the reservoir 14;

As'it may be: periodically necessary to reverse the flow directionthroughthe filter cells 102 to backwash them, the upper end of the mainheader 108 opens into the main supply pipe 96 at 114. The. supply water.may-be divertedfrom'the filter inlet pipe-98 by closing aline'valve116, preferably of the manually operable wafer type, provided thereinand opening a similar valve 118 in the upper portion of the main header108. The backwash water, as indicated by'dotted arrows 120; then entersthe lower portion of eachfilter cell 102through the filter outlet pipes106. Contaminants which have accumulated in the filter cell 102 areflushed upwardly by the'reversed water flow and are-skimmed over to amain backwash outlet pipe -l22.through the filter inlet pipe 98 andintermediate pipes 124 positioned-vat thesurface of the lower layers102, from whence they pass to the waste pipe-26 for deposit in a catchbasin 126 (see FlGl To control the flow through this fluid system, themain backwash outlet pipe 122 has a line valve 128 below theintermediate pipes 124 and a line valve 130 is provided in the unitoutlet pipe 110. It should thus be apparent that during normaloperation, i.e., to accomplish filtering flow 100, the valves 116 and130 should be open and the remaining valves closed. On the other hand,to switch the fluid system to backwashing' flow 120, the valves 118 and128 should be opened and the valves 116 and 130 closed.

In addition to filtering the-processed water, an appropriate amount ofpurifying chemicals such as chlorine may be introduced from thechlorination unit 52 .through'a chlorine conduit 132 to the water as itflows through the unit outlet pipe 112 for bacteria and algae control. v

Referring once again to FIG. 5, the unitoutlet duct l12.has a plurality,of equally spaced outlet'nozzles 134 which are preferably adjustableboth horizontally and vertically. To achieve maximum recirculation ofthe purified water through the reservoir, I prefer to dispose the outletnozzles 134 in such a manner as to utilize the earth's rotational forcesas an aid to the pressure induced .recirculation currents produced bythe unit. It is, therefore, preferred that for use in the SouthernHemisphere'the nozzles 134 be disposed to emit water in a clockwisedirection. For optimum recirculation, the nozzles 134-may also bedisposed to emit the processed water in a slightly downwardly direction.By reintroducing the processed water from a central location in thismanner, the generally concentric recirculation currents produce acentral vortex adjacent the unit 22 and a concomitant hydraulic gradientsloping toward this vortex which causes water from theentire reservoir14 to gravitate toward the centrally located unit 22 to facilitatecontinuous purification of the reservoir water.

As seen in FIGS. 6 and 7, the control chamber 42 is provided to giveeasy access tothe operating components of the unit 22 and is preferablylarge enough to enable a human to move therein. An electrical controlpanel 138, which is connected to the underground power line 26, ismounted on one wall 36 of the control chamber 42. The controls for thesubmersible pump 94 and the air compressor 82 are connected to thecontrol panel 138.The various valves are also positioned in the controlchamber, as well as a viewing port for the mixing chamber formed in thepartition wall 36, while on the other wall 38 viewing ports 142 for-thefilter cells are provided. To allow access to the filter cells .102,filter cell access manholes 144 are also provided in the wall 38. Accessto the mixing chamber 40- is provided by a hatch 146' (FIG. 4) formed'inthe top deck above the mixing chamber. A drainage sump 148' having aconventional drainage pump (not shown) is provided in the floor of thecontrol chamber 42 to eliminate any undesired water from thatchamber.

While the'overall dimensions of the unit 22 may be varied at will, theunit should desirably be constructed to accommodate a flow rateacceptable for-mass water purification purposes and yet be compactenough to be shipped over conventional transportation, e.g., railroadfreight cars or trucks from its point ofmanufacture to the reservoirsite. The unit, therefore, should be capable of processing at least 2000gallons per minute, andpresently available submersible pumps 94 canprocess 4000 gallons per minute through the unit 22 with a headsufficient to set up effective recirculation currents in the reservoir14. c

Having thus described the preferred embodiment of the unit 22, amodified version 22- thereof which not only purifies and recirculatesthe reservoir 14 water but also progressively purifies the remainder 16of the pollutedwater body 10 will now be described with reference toFIG. 9. In accordance with this modification, a bypass conduit 150 isfluidly connected at one end 152 to the main header 108 and extendsthrough the walls 32 where it is connected through a flexible coupling154 to a return conduit 156 passing back to the polluted area 16, Thesize of the bypass conduit 150 is normally such as to bleed offapproximately 5 percent, and preferably no more than [0 percent of thetotal flow through the unit 22 so that purification of the reservoirwater is not impeded. A line valve 158 and flow meter 160 are providedto regulate and indicate the return flow. Moreover, another purifyingchemical adding means indicated at 162 is preferably provided to addappropriate purifying chemicals to the return water. The particularchemicals to be added to the return water depends, of course, on thepollution condition of the water body 10. For example, various types ofweed and algae inhibitors such as a mild copper sulfate solution, may beinjected to progressively deconta'minate the main water body '16. Otherconventional purifying chemicals like acidic or alkaline mixtures mayalso be employed as conditions dictate. I prefer to take the returnwater out of the unit 22'-before chlorine is added to the reservoirwater through the chlorine conduit 132 so that any wild life present inthe main body 16 is not adversely affected.

it should be appreciated that the modified form of the invention may beapplied to many situations in which it is desired to purify pollutedwaters. For example, a number of reservoirs 14 could be constructedalong a polluted riverto provide adjacent communities with pure water.At the same time the constant influx of pure, treated water into theriver would tend to inexpensively decontaminate the entire river flowover a. period of time. Similarly, a lake or pond may be gradually andwholly purified in the same manner.

In light of the above description of the invention, the advantagesachieved thereby will be now briefly reviewed. By preparing a pure waterreservoir from a polluted body of water in accordance with the method ofinvention. a reservoir area may be developed having all of theadvantages of a natural body of water without the need of skilled labor,unusual materials and equipment. The apparatus of the invention may beprefabricated at a remote point, transported to and installed in theprepared site. This unit is entirely self-contained and no externalpiping either for inlet or for outlet purposes must be constructed inthe prepared site. The unit, when working in conjunction with aprefiltering levee, may effectively purify a segment of a polluted bodyof water which would other wise be useless.

As to the particular features of the unit, mobile skimming rings arepreferably provided which can adjust to the varying water levelsfrequently encountered in natural bodies of water. (The unit, of course,may also be usedinartificial pools.)'Moreover, by introducing thepurified water back to the reservoir from its center andby disposing theoutlet nozzles in such a manner as to use the earth's rotational effect,improved recirculation of the purified water is effected. The use of asubmersible pump enables the unit to be compactly designed to facilitateprefabrication and portability while also providing a sufficient flowrate for large scale water purificatton.

Although as described the unit is preferably prefabricated with sheetmetal walls, other conventional prefabricated structures may also beemployed such as preformed concrete structures.

' It is my intention to cover all modifications and equivalents which donot depart from the spirit and scope of this invention as defined by theappended claims.

What I claim is:

l. A water purification unit for purifying a body of water comprising;

a. walls defining a compartment capable of remaining at least partiallysubmerged in the water body;

b. means within said compartment defining a mixing chamber constructedand arranged to contain water at a desired level and a filteringchamber;

c.'skimming means for intaking water from the surface of said water bodyinto said mixing chamber;

d. buoyant means associated with said skimming means to vertically movesaid skimming means in response to water level changes;

e. submerged inlet means for intaking water into said mixing chamberfrom beneath the waters surface; f. vcontrol means including valve meansregulating submerged inlet flow for maintaining the water lever in saidmixing chamber beneath that ofthe water body;

g. filtering means insaid filtering chamber;

h. outlet means opening directly to said water body;

bers secured to said unit to telescopically support said gutter;

wherein said buoyant means are secured to said gutter.

3. The water purification unit of claim 2 in which said buoyant meanscomprises: walls defining an air chamber secured to the bottom of saidgutter; an air compressor fluidly connected to said air chamber; meansfor automatically interconnecting said air compressor and said airchamber to raise said gutter when said gutter is too low relative to thewater surface; and means for automatically exhausting air from said airchamber to lower said gutter when said gutter is too high relative tothe water surface.

4. The water purification unit of claim 1 wherein said watertransferringmeans comprises a submersible pump positioned within said mixing chamberbelow the water body level, conduit means interconnecting the pressureside of said submersible pump and said filtering chamber wherein saidcontrol valve means regulates the flow through said submerged inletmeans to insure a sufficient submerged inlet flow so that saidsubmersible pump is continually submerged.

5. The water purification unit of claim 4 in which said submerged inletfiowre'gulating means comprises: valve means provided between saidsubmerged inlet means and said mixing chamber, said valve means beingresponsive to the level of water in said mixing chamber to insure thatthe submerged inlet flow be. at least 25 percent of the flow throughsaid submersible pump for mixing chamber water levels above thatnecessary to maintain said submersible pump in submergence.

6. The water purification unit of claim 1 in which said outer walls havea substantially flat configuration.

7. The water purification unit of claim 6 in which said outer walls areprefabricated of sheet metal.

8. The water purification unit of claim 1 in which said outlet means aredisposed about the periphery of said outer walls in such a way as to usethe earth's rotational forces to effectuate circulation of the waterthroughout the said body.

9. The water purification unit of claim 4 in which said filtering meanscomprises a plurality of superposed sand filter cells capable offiltering at least 2000 gallons per minute of water,

and wherein said submersible pump has a capacity to deliver 2000 gallonsper minute to said filtering means.

10. The water purification unit of claim 1 which further includes meansfor adding purifying chemicals to the processed water.

2. The water purification unit of claim 1 in which said skimming meanscomprises; a skimming gutter and a plurality of substantially verticallydisposed, extensible support members secured to said unit totelescopically support said gutter; wherein said buoyant means aresecured to said gutter.
 3. The water purification unit of claim 2 inwhich said buoyant means comprises: walls defining an air chambersecured to the bottom of said gutter; an air compressor fluidlyconnected to said air chamber; means for automatically interconnectingsaid air compressor and said air chamber to raise said gutter when saidgutter is too low relative to the water surface; and means forautomatically exhausting air from said air chamber to lower said gutterwhen said gutter is too high relative to the water surface.
 4. The waterpurification unit of claim 1 wherein said water-transferring meanScomprises a submersible pump positioned within said mixing chamber belowthe water body level, conduit means interconnecting the pressure side ofsaid submersible pump and said filtering chamber wherein said controlvalve means regulates the flow through said submerged inlet means toinsure a sufficient submerged inlet flow so that said submersible pumpis continually submerged.
 5. The water purification unit of claim 4 inwhich said submerged inlet flow regulating means comprises: valve meansprovided between said submerged inlet means and said mixing chamber,said valve means being responsive to the level of water in said mixingchamber to insure that the submerged inlet flow be at least 25 percentof the flow through said submersible pump for mixing chamber waterlevels above that necessary to maintain said submersible pump insubmergence.
 6. The water purification unit of claim 1 in which saidouter walls have a substantially flat configuration.
 7. The waterpurification unit of claim 6 in which said outer walls are prefabricatedof sheet metal.
 8. The water purification unit of claim 1 in which saidoutlet means are disposed about the periphery of said outer walls insuch a way as to use the earth''s rotational forces to effectuatecirculation of the water throughout the said body.
 9. The waterpurification unit of claim 4 in which said filtering means comprises aplurality of superposed sand filter cells capable of filtering at least2000 gallons per minute of water, and wherein said submersible pump hasa capacity to deliver 2000 gallons per minute to said filtering means.10. The water purification unit of claim 1 which further includes meansfor adding purifying chemicals to the processed water.